As a podcaster, you have dozens of factors to consider before sending a new episode to your feed, including choosing the right file format. Encoding and storing audio files is one of the major components of uploading podcasts, and there are a variety of podcast file types you can use.

File formats probably aren’t top of mind as you craft your content — if they are, what’s wrong with you? — but they do affect what your listeners end up hearing. The right file format can help make sure your audio sounds good — and that your content is compatible with whatever platforms you’re using.

What is an MP3 audio file?

MP3 — short for MPEG-1 (or MPEG-2) Audio Layer III — is an audio file format designed to compress a sound sequence into a small file size while maintaining playback quality. MP3 is one of the early forms of audio encoding. The MP3 format was especially useful during the days of music CDs, when a lot of data had to fit onto a single disc.

MP3 files come in a constant or variable bit rate, i.e. the rate at which data bits transfer. It’s generally recommended that podcasters use a constant bit rate MP3 for spoken word audio, because it’s the least likely to affect the sound quality. You can choose your bit rate when you first start recording, or select it in your editing program’s export settings during post production. A higher bit rate produces higher quality files, but they take longer to transfer and download, while a lower bit rate means smaller files and shorter downloading times.

There are both benefits and drawbacks to using MP3 files for podcasts:

Pros of MP3s

• Compact and convenient. MP3s are relatively small files, making them easy to upload, download, and transfer. They take up less storage space on devices, and if you host your podcast on your own site, you can save bandwidth and risk fewer streaming interruptions.
• Widely compatible. If you’re uncertain which formats your platform accepts, saving your audio files as MP3 files is the safest bet. MP3s are the most compatible audio file format and are widely accepted by most podcast hosting platforms, including Spotify and Apple Podcasts.

Cons of MP3s

• Lower audio quality. Using an MP3 means you sacrifice audio quality in favor of smaller file sizes, which often means you end up with audio that doesn’t sound quite as good as your original recording. While most listeners probably won’t be able to discern the difference, sharper ears might catch on. One thing to note: Degradation in audio quality is more noticeable with music than with spoken word.
• Prone to distortion. MP3 audio files may add distortion during compression. Since MP3s are a “lossy” type of compression file, they lose a bit of detail from their original recording. Sounds that may not have been present in the original recording — like warbling, rasping, crackling, or ringing — may suddenly appear in audio files after encoding.

What is an AAC audio file?

An AAC file, also known as an Advanced Audio Coding file, is the next generation of the MP3. It uses a “lossy” compression encoder to reduce data size, but offers better quality audio than MP3s at a similar bitrate. Raw AAC audio files usually end with the “.aac” extension, though you might find formatted versions with a “.m4a” extension.

Consider these factors when deciding on an AAC audio file format:

Pros of AACs

• Better sound. AACs have a higher coding efficiency and can therefore withstand compression a bit better than MP3s, resulting in nicer-sounding audio.
• Smaller than MP3s. With slightly smaller file sizes than MP3s, AACs are an excellent choice for streamable and downloadable files. They don’t eat up a lot of bandwidth or data — a win for both you and your dedicated listeners.

Cons of AACs

• Not as widely compatible. Streaming platforms like Spotify don’t accept or play AACs. If you recorded your podcast episode in AAC and want to upload it to one of these platforms, you’ll need to use a program to change the format. (Note that Apple Podcasts uses the AAC format for RSS feed podcasts, but also accepts other formats including MP3s, WAVs, and FLACs.)

Other audio formats for podcasting

Although many streaming platforms don’t accept them, there are other audio formats you can use to record and export your podcast. These are uncompressed, lossless data types, meaning they maintain the audio’s true, original form. These audio file formats have high-quality sound and are great for editing, but they’re generally too large and dense for sharing, streaming, or transferring.

• WAV. Developed by Microsoft and IBM in the 1990s, the Waveform Audio File Format (”.wav”) is a lossless compression encoder that allows listeners to hear audio exactly as it was recorded, including distortion and other compression effects. However, there’s a tradeoff — WAV files are notoriously large and take up a ton of storage space.
• AIFF. Developed by Apple in the late 1980s, AIFF, or the Audio Interface File Format, is another raw audio file format. Like WAVs, AIFFs are storage-intensive and are nearly identical to WAVs in how they store lossless, uncompressed sound. The main difference is AIFFs support ID3 tags — a type of metadata container that holds information like album title names, track or song names, cover art, genres, and more. Note that AIFFs don’t contain timecodes, so they might be slightly more challenging to mix or edit.
• FLAC. The Free Lossless Audio Codec is a lossless compression format that preserves audio in its original high-quality state. FLAC files have the same issue as both WAV and AIFF files — they’re often too big for the job.

Apple Podcasts supports both WAVs and FLACs.

Final thoughts

Your audio will likely sound great regardless of whether you choose MP3 or AAC. While AACs provide slightly better quality than MP3 files, the average listener probably won’t notice a difference. Raw file types like WAVs and AIFFs offer the highest quality sound through lossless compression, but they’re usually too large to easily share with a wide audience. Since AACs aren’t widely compatible across different platforms, MP3s are probably the best way to make sure everyone has access to your show.

And if you recorded your podcast in the wrong format, don’t sweat it. You can always use an audio converter to export your file into a new, better-supported extension.